Many gas turbine engines use a heat exchanger, or recuperator, to increase the operation efficiency of the engine by extracting heat from the exhaust gas and preheating intake air. Typically, a recuperator for a gas turbine engine must be capable of operating at temperatures of between about 500° C. (932° F.) and 700° C. (1292° F.) and internal pressures of between approximately 450 kPa (65.267 psi) and 1400 kPa (203.053 psi) under operating conditions involving repeated starting and stopping.
Generally, recuperators receive compressed, discharged air from a compressor of the engine at opposite sides of a recuperator core. The air flows through air cells towards an air-out duct located between the opposite sides of the recuperator core. Meanwhile, hot exhaust gas flows through exhaust cells that alternate with the air cells and conductively heats the compressed, discharged air.
In some conventional recuperators, the air-out duct is installed in three pieces. First, two wings are welded to the recuperator core. Then, a cap piece is welded to each of the two wings. As a result, the air-out ducts on these conventional recuperators include at least four welds along the entire length of the recuperator core. When exposed to the extreme heat of a recuperator, the welds shrink. This distortion increases stress levels at the air-out duct welds, often resulting in premature failure of the welds, and thus the air-out duct.
In addition, in some conventional recuperators, the air-out duct is placed and welded free-hand, resulting in inexact placement of the duct and poor quality welds. Again, these welds often fail prematurely. These premature failures are of great concern because recuperators are costly to manufacture and not easy to repair once placed in the field. Accordingly, the present invention seeks to address one or more of the above problems by minimizing the number of and improving the quality of welds at the air-out duct of a recuperator.